Keratins are a class of structural proteins widely represented in biological structures, especially in epithelial tissues of higher vertebrates. Keratins may be divided into two major classes, the soft keratins (occurring in skin and a few other tissues) and hard keratins, forming the material of nails, claws, hair, horn and (in birds and reptiles) feathers and scales.
The hard keratins may in turn be further subdivided into structural types described as α-keratin, β-keratin, or feather keratin. Keratins of the α and β types have different predominant structural motifs in their proteins, in the former case supramolecular structures based on the α-helix secondary structure of protein chains, and in the latter case on the β-pleated sheet motif.
All keratins are characterised by a high level of the sulphur-containing diamino-acid cystine, which acts as a cross-linking point between protein chains. This feature of a high-level of interchain crosslinking through cystine gives the keratins, especially the hard keratins, their characteristics of toughness, durability, resistance to degradation, and desirable mechanical properties. Cystine contents vary widely in the keratins, which is reflected in their variation in mechanical properties.
Wool and hair are examples of hard α-keratin. However, even in a given α-keratin, there are many classes of structural protein present, and the mechanical properties arise from a sophisticated supramolecular organisation of proteins of many different types to create a complex morphology with a correspondingly complex mechanical behaviour.
An object of the invention is to provide biopolymer materials derived from soluble keratin derivatives and production methods for producing the biopolymer materials.